Illumination optical unit for a projection exposure apparatus

ABSTRACT

An illumination optical unit for a projection exposure apparatus serves for guiding illumination light toward an illumination field, in which a lithography mask can be arranged. A first facet mirror has a plurality of individual mirrors that provide illumination channels for guiding illumination light partial beams toward the illumination field. The individual mirrors each bear a multilayer reflective coating. A second facet mirror is disposed downstream of the first facet mirror in the beam path of the illumination light. A respective facet of the second facet mirror with at least one of the individual mirrors of the first facet mirror completes the illumination channel for guiding the illumination light partial beam toward the illumination field.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims benefit under35 USC 120 to, international application PCT/EP2013/054404, filed Mar.5, 2013, which claims benefit under 35 USC 119 of German Application No.10 2012 203 950.3, filed Mar. 14, 2012. International applicationPCT/EP2013/054404 also claims priority under 35 USC 119(e) to U.S.Provisional Application No. 61/610,532, filed Mar. 14, 2012. The entiredisclosure of international application PCT/EP2013/054404 and GermanApplication No. 10 2012 203 950.3 are incorporated by reference herein.

The invention relates to an illumination optical unit for a projectionexposure apparatus, in particular for an EUV projection exposureapparatus, for guiding illumination light toward an illumination field,in which a lithography mask can be arranged. Furthermore, the inventionrelates to an illumination system comprising such an illuminationoptical unit, a projection exposure apparatus comprising such anillumination system, a method for producing a micro- or nanostructuredcomponent, in particular a semiconductor chip, with the aid of such aprojection exposure apparatus, and a micro- or nanostructured componentproduced by the method.

An illumination optical unit for an EUV projection exposure apparatus isknown, inter alia, from US 2011/0001947 A1.

It is an object of the present invention to develop an illuminationoptical unit of the type mentioned in the introduction in such a waythat the illumination is adaptable for obtaining an optimum resolutioncapability during the projection exposure.

This object is achieved according to the invention via an illuminationoptical unit for a projection exposure apparatus for guidingillumination light toward an illumination field, in which a lithographymask can be arranged. The unit comprises a first facet mirror having aplurality of individual mirrors that provide illumination channels forguiding illumination light partial beams toward the illumination field,wherein the individual mirrors each bear a multilayer reflectivecoating. The unit also comprises a second facet mirror, which isdisposed downstream of the first facet mirror in the beam path of theillumination light, wherein a respective facet of the second facetmirror with at least one of the individual mirrors of the first facetmirror completes the illumination channel for guiding the illuminationlight partial beam toward the illumination field. The individual mirrorsare arranged such that the respective illumination light partial beam isincident on the individual mirror with an angle of incidence, whereby aplane of incidence is defined. The angle of incidence is predefined suchthat a ratio Rp/Rs is less than 0.8, wherein Rp is the reflectivity forillumination light polarized in the plane of incidence, and Rs is thereflectivity for illumination light polarized perpendicularly to theplane of incidence.

According to the invention, it has been recognized that in particular onaccount of the multilayer reflective coating of the individual mirrors,a polarization selection of the illumination light can be effected via areflection geometry at the individual mirrors. The polarizationselection takes place by virtue of the fact that illumination lightpolarized perpendicularly to the plane of incidence of the reflection atthe respective individual mirror is reflected with preference relativeto illumination light polarized parallel to the plane of incidence. Fromillumination light incident on the facet mirror arrangementsubstantially in an unpolarized manner, illumination light havingillumination light partial beams polarized in a preferred direction canbe generated in this way. It is thereby possible to provide anillumination of the illumination field in which, in particular dependingon the illumination angle, that polarization which is required forfulfilling demanding resolution stipulations is used in each case in atargeted manner. The ratio Rp/Rs can be less than 0.7, can be less than0.6, can be less than 0.5, can be less than 0.4, can be less than 0.3,can be less than 0.2, can be less than 0.1, can be less than 0.05, canbe less than 0.02, can be less than 0.01, can be less than 1×10⁻³, canbe less than 1×10⁻⁴ and can be less than 1×10⁻⁵. In particular, theratio Rp/Rs can be exactly 0; therefore, that component of therespective illumination light partial beam which is polarized in theplane of incidence can be completely suppressed via the reflection atthe respective individual mirror. In general, a facet of the secondfacet mirror together with a group of individual mirrors of the firstfacet mirror completes a group illumination channel to which the facetof the second facet mirror and a group of individual mirrors of thefirst facet mirror belong. Such an arrangement is known, in principle,from US 2011/0001947 A1. The ratio Rp/Rs can be predefined via the angleof incidence of the respective illumination light partial beam on theindividual mirror and, depending on the construction of the multilayerreflective coating, is sensitively dependent on the angle of incidence.

Angles of incidence at which the respective illumination light partialbeam is incident on the individual mirror deviates by a maximum of 25°from a Brewster angle IB of the multilayer reflective coating areparticularly suitable for predefining a ratio Rp/Rs that givespreference to the polarization component oscillating perpendicularly tothe plane of incidence. A deviation of the angle of incidence from theBrewster angle can be less than 20°, can be less than 10°, can be lessthan 5°, can be less than 3°, can be less than 2° or can be less than1°. In particular, the angle of incidence can correspond exactly to theBrewster angle.

The individual mirrors can be arranged on an individual-mirror carrierembodied rotationally symmetrically with respect to an axis of incidenceof the illumination light incident on the first facet mirror, and/or thefacets of the second facet mirror are arranged on a facet carrierembodied rotationally symmetrically with respect to an axis (k) ofincidence of the illumination light incident on the first facet mirror.Such carriers arranged rotationally symmetrically make possiblereflection geometries for the illumination light partial beams at thefacet mirrors for which angles of incidence are used which deviate onlyslightly from an average angle of incidence, the average angle ofincidence then being that which is used for predefining the desiredratio Rp/Rs.

A ring-shaped facet carrier makes possible, in particular, a tangentialpolarization in the illumination of the illumination field, in the caseof which an object in the illumination field can be illuminated in amanner polarized perpendicularly to the plane of incidence of theillumination light on the object, independently of the illuminationangle.

The illumination optical unit can be embodied such that a section of theillumination field that is less than 80% of the total illumination fieldis illuminated via an illumination channel via which the illuminationlight is guided via a facet of the second facet mirror. Suchsection-by-section of the illumination field makes possible anarrangement of the illumination optical unit in the manner of thespecular reflector, as is known, apart from the polarizationpredefinition, for example from US 2006/0132747 A1. The illuminatedsection of the illumination field can be less than 50% of the totalillumination field or can be even smaller, e.g. ⅓, ¼, ⅙, or can comprisean even smaller fraction of the total illumination field.

The advantages of an illumination system including such an illuminationoptical system, of a projection exposure apparatus including such anillumination system, of a production method using such a projectionexposure apparatus, and of a component made by such a method correspondto those which have already been explained above with reference to theillumination optical unit according to the invention. The component canbe produced with extremely high structural resolution. By way ofexample, a semiconductor chip with an extremely high integration densityor storage density can be produced in this way.

Exemplary embodiments of the invention are explained in greater detailbelow with reference to the drawing. In which:

FIG. 1 schematically shows a meridional section through a projectionexposure apparatus for EUV projection lithography, the illustrationshowing illumination light guidance in an illumination optical unitschematically and not according to the invention;

FIG. 2 likewise shows in a meridional section an excerpt from anembodiment according to the invention of the illumination optical unitin the region of beam guiding of illumination light via two facetmirrors of the illumination optical unit toward an illumination field;

FIG. 3 shows an excerpt enlargement in the region of the detail III inFIG. 2;

FIG. 4 shows in a diagram a dependence of a reflection R of theillumination light on an angle I of incidence on an individual mirror ofa first facet mirror of the illumination optical unit according to FIG.2, plotted firstly for illumination light (S) polarized perpendicularlyto the plane of incidence and for illumination light (P) polarizedparallel to the plane of incidence;

FIG. 5 shows, in an illustration similar to FIG. 2, a further embodimentof the illumination optical unit, wherein illumination light partialbeams that are guided via facets of a second facet mirror of theillumination optical unit in each case illuminate a section of theillumination field, that is to say not the total illumination field;

FIG. 6 shows the illumination optical unit according to FIG. 2, theillustration additionally showing a polarization distribution of anillumination of a field point of the illumination field depending on theillumination angle (tangential polarization); and

FIG. 7 shows a plan view of the polarization distribution according toFIG. 6.

FIG. 1 schematically shows a projection exposure apparatus 1 formicrolithography in a meridional section. The projection exposureapparatus 1 includes a light or radiation source 2. An illuminationsystem 3 of the projection exposure apparatus 1 has an illuminationoptical unit 4 for exposing an illumination field coinciding with anobject field 5 in an object plane 6. The illumination field can also belarger than the object field 5. An object in the form of a reticle 7,which is arranged in the object field 5 and which is held by an objector reticle holder 8, is exposed in this case. The reticle 7 is alsodesignated as a lithography mask. The object holder 8 is displaceablealong a displacement direction via an object displacement drive 9. Aprojection optical unit 10 serves for imaging the object field 5 into animage field 11 in an image plane 12. A structure on the reticle 7 isimaged onto a light-sensitive layer of a wafer 13 arranged in the regionof the image field 11 in the image plane 12. The wafer 13 is held by awafer holder 14. The wafer holder 14 is likewise displaceable along thedisplacement direction in a manner synchronized with the object holder 8via a wafer displacement drive 15.

The radiation source 2 is an EUV radiation source having an emitted usedradiation in the range of between 5 nm and 30 nm. This can involve aplasma source, for example a GDPP source (Gas Discharge-Produced Plasma)or an LPP source (Laser-Produced Plasma). A radiation source based on aSynchrotron or on a Free Electron Laser (FEL) can also be used for theradiation source 2. Information concerning such a radiation source canbe found by the person skilled in the art for example from U.S. Pat. No.6,859,515 B2. EUV radiation 16 emerging from the radiation source 2 isconcentrated by a collector 17. A corresponding collector is known fromEP 1 225 481 A. Downstream of the collector 17, the EUV radiation 16propagates through an intermediate focal plane 18 before it impinges ona field facet mirror 19. The field facet mirror 19 is a first facetmirror of the illumination optical unit 4. The first facet mirror 19 hasa multiplicity of individual mirrors (not illustrated in FIG. 1). Thefirst facet mirror 19 is arranged in a plane of the illumination opticalunit 4 which is optically conjugate with respect to the object plane 6.

The EUV radiation 16 is hereinafter also designated as illuminationlight or as imaging light. The illumination light 16 is incident on thefirst facet mirror 19 in an unpolarized manner, that is to say with auniformly distributed polarization. Upstream of the first facet mirror19, therefore, polarization vectors of the illumination light 16oscillate perpendicularly to the axis k of incidence in a mannerdistributed uniformly in all directions parallel to the xy plane.

Downstream of the first facet mirror 19, the EUV radiation 16 isreflected by a pupil facet mirror 20. The pupil facet mirror 20 is asecond facet mirror of the illumination optical unit 4. The pupil facetmirror 20 is arranged in a pupil plane of the illumination optical unit4 which is optically conjugate with respect to the intermediate focalplane 18 and with respect to a pupil plane of the projection opticalunit 10 or coincides with the pupil plane. The pupil facet mirror 20 hasa plurality of pupil facets (not illustrated in FIG. 1). With the aid ofthe pupil facets of the pupil facet mirror 20 and a downstream imagingoptical assembly in the form of a transfer optical unit 21 havingmirrors 22, 23 and 24 designated in the order of the beam path,individual mirror groups of the field facet mirror 19 are imaged intothe object field 5. The last mirror 24 of the transfer optical unit 21is a mirror for grazing incidence (“grazing incidence mirror”).

In order to facilitate the description of positional relationships, FIG.1 depicts a Cartesian xyz coordinate system as a global coordinatesystem for describing the positional relationships of components of theprojection exposure apparatus 1 between the object plane 6 and the imageplane 12. In FIG. 1, the x-axis runs perpendicularly to the plane of thedrawing into the latter. In FIG. 1, the y-axis runs toward the right andparallel to the displacement direction of the object holder 9 and of thewafer holder 14. In FIG. 1, the z-axis runs downward, that is to sayperpendicularly to the object plane 6 and to the image plane 12.

The x-dimension over the object field 5 or the image field 11 is alsodesignated as field height.

In the case of the projection exposure apparatus 1 according to FIG. 1,the field facet mirror 19 is the first facet mirror and the pupil facetmirror 20 is the second facet mirror in the beam path of theillumination light 16. The facet mirrors 19, 20 can also interchangetheir function. Thus, the first facet mirror 19 can be a pupil facetmirror, which is then arranged in a pupil plane of the projectionoptical unit 10 or in a conjugate plane with respect thereto, and thesecond facet mirror 20 can be a field facet mirror, which is thenarranged in a field plane which is optically conjugate with respect tothe object plane 6.

In the case of the illumination optical unit 25, the first facet mirror19 has a plurality of individual mirrors 26 that provide illuminationchannels for guiding illumination light partial beams 16, toward theobject field or illumination field 5. The individual mirrors 26 arearranged on an individual-mirror carrier 27. The individual-mirrorcarrier 27 is embodied rotationally symmetrically with respect to anaxis k of incidence of the illumination light 16, the axis runningparallel to the z-axis. The individual-mirror carrier 27 is embodiedwith a round carrier surface 28 arranged parallel to the xy plane. Theindividual-mirror carrier 27 lies between the incident illuminationlight 16 and the object field 5.

The individual mirrors 26 can have square or rectangular reflectivesurfaces arranged in a densely packed manner on the individual-mirrorcarrier 27. Other forms of individual mirrors which enable thereflective surface of the first facet mirror 19 to be occupied as far aspossible without any gaps can also be used. Such alternativeindividual-mirror forms are known from the mathematical theory ofparqueting. In this connection, reference should be made to thereferences indicated in US 2011/0001947 A1.

Depending on the embodiment of the first facet mirror 19, the individualmirrors 26 have x/y extents in the range of, for example, from 100μm×100 μm to, for example, 5 mm×5 mm. The individual mirrors 26 can beshaped such that they have a concentrating effect for the illuminationlight 16.

The individual mirrors 26 can have an arrangement on theindividual-mirror carrier 27 which is rotationally symmetrical withrespect to the axis k of incidence of the illumination light 16. Thearrangement can be embodied, for example, in a plurality of concentricrings of individual mirrors 26 on the individual-mirror carrier 27,wherein the center of this individual-mirror arrangement coincides withan intersection point of the axis k of incidence of the illuminationlight 16 through the carrier surface 28.

The meridional section according to FIG. 2 illustrates by way of examplefour of the individual mirrors 26. In a real embodiment of a first facetmirror 19, the number of individual mirrors 26 is very much higher.Overall, the first facet mirror 19 has several hundred to severalthousand of the individual mirrors 26.

A total reflective surface of the first facet mirror 19, composed of thereflective surfaces of the individual mirrors 26, has an extent of, forexample, 300 mm×300 mm or 600 mm×600 mm, depending on the embodiment ofthe first facet mirror 19.

Each of the individual mirrors 26, for individually deflecting impingingillumination light 16, is respectively connected to an actuator 29, asindicated on the basis of the topmost individual mirror 26 illustratedin FIG. 2. The actuators 29 are arranged on that side of each of theindividual mirrors 26 which faces away from a reflective side of theindividual mirrors 26. The actuators 29 can be embodied, for example, aspiezoactuators. Configurations of such actuators are known from theconstruction of micromirror arrays.

Each of the individual mirrors 26 can be individually tiltedindependently about two mutually perpendicularly tilting axes, wherein afirst of the tilting axes runs parallel to the x-axis and the second ofthe two tilting axes runs parallel to the y-axis. The two tilting axeslie in the individual reflective surfaces of the respective individualmirrors 26.

The reflective surfaces of the individual mirrors 26 bear multilayerreflective coatings. FIG. 3 shows an excerpt enlargement in the regionof a reflective surface of one of the individual mirrors 26. Reflectivelayers 31, 32 are applied on an individual-mirror main body 30, whichlayers can be alternate layers composed of molybdenum (Mo) and silicon(Si). FIG. 3 illustrates by way of example a bilayer 31, 32 comprisingin each case one Mo layer and Si layer. A total reflective coating 33can have a plurality of such bilayers 31, 32, for example 5, 10, 20, 30or even more bilayers of this type.

The individual mirrors 26 of the first facet mirror 19 are arranged suchthat the respective illumination light partial beam 16, is incident onthe individual mirror 26 with an angle I of incidence with respect to anormal N to the individual-mirror reflective surface which, upon thereflection of the illumination light partial beam 16, at the individualmirror 26, gives preference to an s-polarization in comparison with ap-polarization. The s-polarization concerns the direction ofpolarization of the illumination light partial beam 16, which oscillatesperpendicularly to the plane of incidence (plane of the drawing in FIG.3) of the individual mirror 26. The p-polarization concerns thatpolarization of the illumination light partial beam 16, which oscillatesin the plane of incidence of the individual mirror 26. Thes-polarization is indicated by crossed-through circles in FIG. 2. Thep-polarization is indicated by a double-headed arrow arrangedperpendicularly to the axis k of incidence in FIG. 2. The s-polarizationis represented by large dots on the beam path of the illumination lightpartial beam 16 _(i) in FIG. 3. The p-polarization is represented bydouble-headed arrows on the beam path of the illumination light partialbeam 16 _(i). The preference given to s-polarization relative top-polarization upon the reflection of the illumination light partialbeam 16 _(i) at the individual mirror 26 is such that a ratio Rp/Rsbetween a reflectivity Rp for the p-polarized illumination light 16 anda reflectivity Rs for the s-polarized illumination light 16 is less than0.8. This preference given to s-polarization is illustrated in FIG. 3 bythe fact that after the reflection of the illumination light partialbeam 16 _(i) at the individual mirror 26, the p-polarization componentis represented by a shorter double-headed arrow in comparison with theincident illumination light partial beam 16 _(i) the intensity of thes-polarization component being influenced less by the reflection at theindividual mirror 26, which is illustrated by dots on the reflected beampath of the reflected illumination light partial beam 16 _(i) which arethe same size as the dots on the incident beam.

The dependence of the reflectivities Rs, Rp on the angle I of incidenceis illustrated in FIG. 4.

Rs rises in the case of an angle of incidence of I=0° (normal incidence)from a value of 0.6R₀ monotonically up to a maximum value R_(o) in thecase of an in practice maximum angle of incidence of 85°.

The reflectivity Rp falls proceeding from the value 0.6 R₀ in the caseof the angle of incidence of I=0° firstly monotonically down to areflectivity Rp=0 in the case of a Brewster angle I_(B) of incidence,which is in the region of an angle of incidence of 45°. For angles ofincidence of I>I_(B), the reflectivity Rp rises monotonically again upto a value of approximately 0.8 R₀ in the case of the in practicemaximum angle of incidence of approximately 85°. The ratio Rp/Rs is lessthan 0.8 in a range of angles I of incidence starting from a value ofapproximately I>20°. For angles I of incidence in the region of theBrewster angle I_(B), the ratio becomes continuously smaller, dependingon how close the actual angle I of incidence is to the Brewster angleI_(B). At the Brewster angle I_(B) itself, the ratio Rp/Rs is 0.

Depending on the arrangement of the individual mirror 26, the angle I ofincidence on the individual mirror 26 can be predefined so as to resultin a ratio Rp/Rs which is less than 0.7, which is less than 0.6, whichis less than 0.5, which is less than 0.4, which is less than 0.3, whichis less than 0.2, which is less than 0.1, which is less than 0.05, whichis less than 0.02, which is less than 0.01, which is less than 1×10⁻³,which is less than 1×10⁻⁴, which is less than 1×10⁻⁵ or which is evensmaller still.

For the angle I of incidence at which the respective illumination lightpartial beam 16, is incident on the respective individual mirror 26,depending on the orientation of the individual mirror 26, it is possibleto achieve a predefined value I-I_(B), that is to say a deviation withrespect to the Brewster angle I_(B), whose absolute value is less than25°, less than 20°, less than 10°, less than 5°, less than 3°, less than2°, less than 1° and in particular is exactly at the Brewster angleI_(B).

These predefined values for the angles I of incidence can be monitoredon a central control device 34 of the illumination optical unit 25,which is signal-connected to the actuators 29 of the individual mirrors26 in a manner not illustrated. Via a look-up table, the predefinedvalues can also be linked to desired values for the reflectivity ratioRp/Rs to be achieved.

The second facet mirror 20 is disposed downstream of the first facetmirror 19 in the beam path of the illumination light 16 (cf. FIG. 2). Arespective facet 35 of the second facet mirror 20 with at least one ofthe individual mirrors 26 of the first facet mirror 19 completes theillumination channel for guiding the illumination light partial beams16, toward the illumination field 5. In general, the arrangement is suchthat one of the facets 35 of the second facet mirror 20 together with agroup of individual mirrors 26 of the first facet mirror 19 completes agroup illumination channel for a plurality of partial beams 16, to whichthe facet 35 of the second facet mirror 20 and a group of individualmirrors 26 of the first facet mirror 19 belong. This group of individualmirrors 26 of the first facet mirror 19 therefore guides illuminationlight partial beams 16 _(i) all via exactly the same facet 35 of thesecond facet mirror 20 toward the illumination field 5.

Via the reflection of the illumination light partial beam 16, at thefacet 35 of the second facet mirror 20, the s-polarization of theillumination light partial beam 16, is once again given preference,since here, too, a reflection takes place with an angle I of incidencethat differs significantly from 0. This preference given to thes-polarization is also indicated in FIG. 2, where the s-polarization ofthe illumination light 16 is illustrated by a crossed-through circle andthe p-polarization is illustrated by a double-headed arrow perpendicularto the axis k of incidence and lying in the plane of the drawing in FIG.2. The double reflection of the illumination light partial beam 16, onceat one of the individual mirrors 26 and a second time at one of thefacets 35 of the second facet mirror 20 results in an almost complete oreven entirely complete s-polarization in the case of the illuminationlight partial beam 16, impinging on the illumination field 5.

The facets 35 of the second facet mirror 20 are arranged on a facetcarrier 36, which is indicated in a dashed manner in FIG. 2. The facetcarrier 36 is embodied in a ring-shaped fashion. The facet carrier 36 isembodied rotationally symmetrically with respect to the axis k ofincidence of the illumination light 16. The arrangement of the facets 35of the second facet mirror 20 on the facet carrier 36 is correspondinglyrotationally symmetrical.

The illumination optical unit 25 is arranged overall rotationallysymmetrically with respect to the axis k of incidence. The axis k ofincidence passes through a center of the illumination field 5. The axisk of incidence is perpendicular to the object plane 6.

The rotational symmetry of the arrangement of the individual mirrors 26of the first facet mirror 19 and of the facets 35 of the second facetmirror 20 makes possible a beam guidance of the illumination lightpartial beams 16 _(i) that is rotationally symmetrical to a goodapproximation in any case with respect to the axis k of incidence.

Facets 35 of the second facet mirror 20 which are provided forreflecting illumination light partial beams 16 _(i) which are deflectedby individual mirrors 26 of the first facet mirror 19 in the xz planeare illustrated in a dashed manner in FIG. 2 at the level of the axis kof incidence. On account of the ring-shaped design of the facet carrier36, the field facets 35 are situated, of course, in a manner spacedapart from the axis k of incidence both in the positive and in thenegative x-direction correspondingly with respect to the plane of thedrawing in FIG. 2. Corresponding facets 35 are arranged in a mannerdistributed uniformly in the circumferential direction around the axis kof incidence on the facet carrier 36, thus resulting in thefundamentally rotationally symmetrical reflection arrangement for theillumination light partial beams 16 _(i). An illumination withtangentially polarized illumination light 16 results for each point onthe illumination field 5. This is illustrated in greater detail for anillumination field point 37 in FIGS. 6 and 7.

From every illumination direction, the illumination light 16 impinges onthe illumination field point 37 in an s-polarized manner. Since, onaccount of the ring-shaped arrangement of the field facets 35, theillumination field point 37 is illuminated with a ring-shapedillumination angle distribution 38 (the illumination field point 37“sees” a ring-shaped light source), there arises at every location ofthis ring-shaped illumination angle distribution 38, indicated by acircle in FIG. 7, an s-polarization that is supplemented to form atangential polarization. At every location of the ring-shapedillumination angle distribution 38, a polarization vector 39 oscillatestangentially with respect to the illumination angle distribution 38.

On account of this tangential polarization, the reticle 7 in theillumination field 5 can be illuminated with s-polarized illuminationlight 16 independently of the illumination angle. This illuminationmakes possible an optimized structural resolution when the illuminationoptical unit 25 is used as part of the projection exposure apparatus 1.

With the illumination optical unit 25, the illumination field 5 can beilluminated with illumination angles that are greater than a lower limitvalue for the illumination angle, which is predefined by a centralshading of the beam path of the illumination light 16 that is predefinedby the individual-mirror carrier 27.

With the illumination optical unit 25, it is possible to realize anannular illumination setting or else a multipole illumination setting,e.g. a dipole illumination setting or a quadrupole illumination setting,e.g. a C-Quad illumination setting.

FIG. 5 shows a further embodiment of an illumination optical unit 40,which can be used instead of the illumination optical unit 25.Components corresponding to those which have already been explainedabove with reference to FIGS. 1 to 4 and 6 and 7 bear the same referencenumerals and will not be discussed in detail again.

In the case of the illumination optical unit 40, the illumination light16 is guided such that a section 5, of the illumination field 5 that isless than 80% of the total illumination field 5 is illuminated via anillumination channel via which the illumination light 16 is guided viaone of the facets 35 of the second facet mirror 20. The illuminationfield section 5, can cover 50% of the total illumination field 5 or aneven smaller fraction, that is to say e.g. ⅓,¼,⅙, or else an evensmaller fraction, e.g. 1/10, 1/20, or 1/50, of the total illuminationfield 5.

The illumination optical unit 40 can be embodied, with regard to thearrangement of the two facet mirrors 19, 20, in the manner of a specularreflector which, apart from the polarizing effect of the individualmirrors 26 and the facets 35, is known from US 2006/0132747 A1.

In the case of the embodiment according to FIG. 5, the illuminationfield section 5, has, in the y-direction, approximately one quarter ofthe y-extent of the total illumination field 5.

During projection exposure with the aid of the projection exposureapparatus 1, at least one part of the reticle 7 in the object field 5 isimaged onto a region of the light-sensitive layer onto the wafer 13 inthe image field 11 for the lithographic production of a micro- ornanostructured component, in particular of a semiconductor component,for example of a microchip. In this case, the reticle 7 and the wafer 13are moved in a temporally synchronized manner in the y-directioncontinuously in scanner operation.

1-10. (canceled)
 11. An illumination optical unit configured toilluminate an illumination field with illumination light, theillumination optical unit comprising: a first facet mirror comprising aplurality of individual mirrors, each individual mirror comprising amultilayer reflective coating; a second facet mirror comprising aplurality of individual facets, wherein: the second facet mirror isdownstream of the first facet mirror along a path of the illuminationlight to the illumination field; each individual mirror of the firstfacet mirror is configured to guide a respective illumination lightpartial beam to the illumination field via a respective facet of thesecond facet mirror; and each individual mirror of the first facetmirror is configured so that its respective illumination light partialbeam is incident on the individual mirror with an angle of incidence sothat a ratio of a reflectivity of the individual mirror for illuminationlight polarized in a plane of incidence of the illumination light on theindividual mirror to a reflectivity of the individual mirror forillumination light polarized perpendicular to the plane of incidence ofthe illumination light on the individual mirror is less than 0.7. 12.The illumination optical unit of claim 11, wherein each facet of thesecond mirror is configured to guide more than one illumination partialbeam.
 13. The illumination optical unit of claim 11, wherein, for eachindividual mirror, the angle of incidence is within 20° of a Brewsterangle of the multilayer reflective coating of the individual mirror. 14.The illumination optical unit of claim 13, further comprising a firstcarrier, wherein each individual mirror is rotationally symmetricallyarranged on the first carrier with respect to an axis of incidence ofthe illumination light incident on the first facet mirror.
 15. Theillumination optical unit of claim 14, further comprising a secondcarrier, wherein each facet of the second facet mirror is rotationallysymmetrically arranged on the second carrier with respect to an axis ofincidence of the illumination light incident on the first facet mirror.16. The illumination optical unit of claim 15, wherein the secondcarrier is ring-shaped.
 17. The illumination optical unit of claim 15,wherein the illumination optical unit is configured so that a section ofthe illumination field that is less than 80% of the total illuminationfield is illuminated via an illumination channel via which theillumination light is guided via a facet of the second facet mirror. 18.The illumination optical unit of claim 13, wherein the illuminationoptical unit is configured so that a section of the illumination fieldthat is less than 80% of the total illumination field is illuminated viaan illumination channel via which the illumination light is guided via afacet of the second facet mirror.
 19. The illumination optical unit ofclaim 11, further comprising a first carrier, wherein each individualmirror is rotationally symmetrically arranged on the first carrier withrespect to an axis of incidence of the illumination light incident onthe first facet mirror.
 20. The illumination optical unit of claim 19,further comprising a second carrier, wherein each facet of the secondfacet mirror is rotationally symmetrically arranged on the secondcarrier with respect to an axis of incidence of the illumination lightincident on the first facet mirror.
 21. The illumination optical unit ofclaim 20, wherein the second carrier is ring-shaped.
 22. Theillumination optical unit of claim 20, wherein the illumination opticalunit is configured so that a section of the illumination field that isless than 80% of the total illumination field is illuminated via anillumination channel via which the illumination light is guided via afacet of the second facet mirror.
 23. The illumination optical unit ofclaim 11, further comprising a carrier, wherein each facet of the secondfacet mirror is rotationally symmetrically arranged on the carrier withrespect to an axis of incidence of the illumination light incident onthe first facet mirror.
 24. The illumination optical unit of claim 23,wherein the carrier is ring-shaped.
 25. The illumination optical unit ofclaim 23, wherein the illumination optical unit is configured so that asection of the illumination field that is less than 80% of the totalillumination field is illuminated via an illumination channel via whichthe illumination light is guided via a facet of the second facet mirror.26. The illumination optical unit of claim 11, wherein the illuminationoptical unit is configured so that a section of the illumination fieldthat is less than 80% of the total illumination field is illuminated viaan illumination channel via which the illumination light is guided via afacet of the second facet mirror.
 27. The illumination optical unit ofclaim 26, wherein, for each individual mirror, the angle of incidence iswithin 20° of a Brewster angle of the multilayer reflective coating ofthe individual mirror.
 28. An illumination system, comprising: anillumination optical unit according to claim 11; and a projectionoptical unit configured to image an object field arranged in theillumination field into an image field.
 29. An apparatus, comprising: anEUV light source configured to generate illumination light; anillumination optical unit according to claim 11; and a projectionoptical unit configured to image an object field arranged in theillumination field into an image field.
 30. A method of operating aprojection exposure apparatus comprising an illumination optical unitand a projection optical unit, the method comprising: using theillumination optical unit to illuminate at least some structures of areticle; and using the projection optical unit to image at least some ofthe illuminated structure onto a light-sensitive material, wherein theprojection optical unit comprises a projection optical unit according toclaim 11.